Treatment of soap



United rates Patent i TREATMENT OF SOAP Louis Coetzer, Rynfield, Benoni, Transvaal, Union of South Africa, and Edward Anthony Wainwright, Durban, Natal, Union of South Africa, assignors to Lever Brothers Company, New York, N. Y., a corporation of Maine No Drawing. Application June 15, 1955, Serial No. 515,791

Claims priority, application Great Britain June 16, 1954 8 Claims. (Cl. 252-367) This invention relates to the treatment of soap, particularly extruded soap of at least 20% moisture content.

It has been found that the hardness of bars or tablets (hereinafter collectively referred to as bars) of such soap, which have been obtained by extruding the soap at a temperature not exceeding 35 C., is increased by heating them by means of alternating current to a temperature of at least 40 C. but below that at which the soap becomes no longer form-retaining due to melting and then allowing them to cool.

According to the invention there is provided a process of hardening a bar of at least 20% moisture content soap obtained by extruding the soap at a temperature not ex ceeding 35 C. which comprises heating the bar by means of alternating current to a temperature of at least 40 C. but below that at which the soap becomes no longer fonnretaining due to melting and then allowing the bar to cool.

Preferably, the soap contains at least 25% moisture. The invention has been found particularly useful with genuine soaps having a total fatty matter content of 60-65% The invention may also be applied to filled soaps, in particular those which contain no more than 50% moisture.

The most useful field of application of the invention is that of soap bars which have been extruded at relatively low temperatures, having regard to their moisture content, for example 25 to 30 C. in the case of genuine soaps of about 30% moisture content. The hardening effect of the process of the invention has, in general, been found most marked with those soaps which exhibit undue softening at the temperature of extrusion. Thus, for example, with genuine soaps of about 30% moisture content extruded at 25 to 30 C., the invention is most useful with soaps from fat charges containing a high percentage of low or medium titre tallow or a high percentage of rosin.

In general, the higher is the temperature to which the bar is heated the greater is the increase in hardness. It is frequently found that the rate of increase of hardness rises steeply as the melting point is approached. However, the practical difiiculty of heating the soap uniformly to within a few degrees of the melting point without any substantial portion actually melting militates against working too close to this point. Also, although the lathering properties of the soaps are not usually appreciably affected by heating to temperatures in the lower portion of the range given, the increase in hardness tends to be accompanied by a sharp decrease in ease of lathering as the melting point is approached. A suitable temperature for any particular soap can easily be determined by heating samples to different temperatures, allowing them to cool, and measuring their hardness and lathering power. As a rule, temperatures within the range 45 to 55 C. have been found to be most suitable.

Once the required temperature has been reached, the soap can be allowed to cool, as there is usually little advantage to be gained by maintaining the soap at this temperature for any length of time. It is dificult to accelerate the rate of cooling of the soap. An average-size bar may take 1 to 2 hours to cool.

2,802,793 Patented Aug. 13, 1957 The heating may be resistance heating by means of a low frequency alternating current, such as mains frequency current, or dielectric heating by high frequency alternating current, such as radio frequency current. The heating may be carried out batchwise by placing each bar between a pair of electrodes or continuously by passing the bar between moving endless-belt electrodes. Alternatively, the bars may be heated in the stamping dye by using opposite faces of the dye as electrodes.

The time required to reach any given temperature depends upon the nature of the soap, the thickness of the bar and, in varying degrees, depending on the mode of heating, on the potential applied, the current passing and the frequency of the current used.

It has been found that, as a general rule, the more rapid is the heating to the required temperature, the greater is the increase in hardness.

There may be some small loss of moisture during heating and this may tend to increase the hardness slightly but the major part of the increase in hardness is not due to this cause, as can be demonstrated by carrying out theprocess under conditions which prevent any loss of moisture.

In the following examples, which illustrate the invention, bars of soap 45.7 x 5.7 x 0.79 cm. were used. These bars were produced by rapidly chilling the molten soap, milling it, and then plodding under reduced pressure at 25 to 30 C. and cutting the plodded bar. The heating was carried out by clamping the bar of soap between two metal electrodes, one at each end, with an average current of 2 amps. (the current increases as the conductivity of the soap increases with temperature) at 230 volts and 50 cycles per second. The bars took approximately 2 /2 to 3 minutes to reach the required temperature. Heating was discontinued when the soap had reached the required temperature and the soap was then allowed to cool.

The hardness of the soaps was determined 24 hours after heating by measuring the force required to pull a wire through the soap under standardised conditions. The bars were weighed before and after treatment. Control bars, that is bars not heated according to the invention, were kept in moisture-proof wrappers and their hardness measured at the same time as that of the treated bars.

Example 1 Soap fat charge: Percent Palm oil 79.5 Olive oil 0.5 Palm kernel oil 17.0 Rosin 3.0 Fatty matter content 62.2

Hardness Loss in Heated Weight to O. Percent 1b. at O.

Control Bar 6. 9 21 0.2 Hardened Bar 50 9.0 21 0. 6

Example 2 Soap fat charge: Percent Palm kernel oil 67 Tallow 23 Rosin 10 Fatty matter content 65.3

Hardness Loss in Heated Weight to O. Percent lb. at C.

Control bar 4. 6 l8 Hardened Bar 6. 6 18 O. 3 Do 6.6 18 0.3

- Fatty matter content Example 3 Soap fat charge: Percent Tallow (41 titre) 80 Palm kernel oil 17 Rosin v3 Fatty matter content 64.5

Hardness i Loss in Heated Weight to C. Percent lb. at C.

Control Bar '4. 2 20 0. 2 5 49' 5.3 -19 0.4 47 5.1 19 0.4 45 4.9 19 0.4 43 4.6 19 0.4

;Example4 Soap fat charge: Percent Palm .oil 80 Palm kernel o l 17 vRosin 3 Fatty matter content 61.5

Hardness Loss in Heated Weight to C. Percent lb. at

Control Bar 7.2 20.5 0.3 Hardened Bar 50 9. 0 20 0.6 Do 40 8.2 20 0.6

Example Soap fat charge: Percent Coconut oil 80 Tallow 20 Fatty matter content 63.0

Hardness Loss in Heated Weight to C. Percent 1b. at C.

Control Bar 6. 7 21. 6 0. 3 43 7.8 21.5 0.6 53 8.5 21.5 0.6

Example 6 Soap fat charge: Percent Palm oil 80 Palm. kernel. oil 17 Rosin 3 Fatty matter content 61.6

Hardness Loss in Heated Weight to 0 Percent lb. at C.

Control Bar 7. 9 20 0.5 52 10.7 20 0.8 .49 9.3 20 0.7 46 9.7 20 0.7 43 9.4 20 0.6 -40 9.4 20 0.6

Example 7 Soap fat charge: Percent Tallow 63 Groundnut oil Coconut oil 'Rosin 2 Hardness Loss in Heated Weight to C. Percent 1b. at C.

Control Bar 5. 9 20 0. 1 7.5 20 0.3 6.9 20 0.4 6.7 20 0.3 6.7 20 0.3 6.6 20 0.3

Soap fat charge: Percent Palm kernel oil 67 Tallow 23 Rosin 10 Fatty matter content 62.5

Hardness Loss in Heated Weight to C. Percent lb. at C.

Control Bar 4. 8 18 0.3 Hardened Bar. 52 9. 7 18 0. 5 Do 49 8.1 18 0.5 Do 46 6.9 18 0.4 Do 43 6.7 18 0.4 Do 40 6.7 18 0.3

Example 9 Soap fat charge: Percent Prime tallow (41.5 titre) Coconut oil 10 Fatty matter content 45.4 Alkaline sodium silicate Tw 1.5 Sodium carbonate 0.24

Hardness Heated to C.

lb. at C.

Control Bar 2. O 24. 5 Hardened Bar 43. 3 4. 0 26. 7 Do 46.1 4.9 26.7 Do. 48.9 5.3 26.7 Do 51.7 6.3 26.7 Do 54.4 7.2 26.7

Example 10 Soap fat charge: Percent Prime tallow (41.5 titre) 82 Coconut oil 18 Fatty matter content 46.2 Alkaline sodium silicate 140 tw 1.5 Sodium carbonate 0.2

Hardness Heated to C.

115. at C.

Control Ban..- 2. 3 22 Hardened Bar 51.0 7. 6 22 Do 48.9 6.5 22

Example 11 Soap fat charge: Percent Prime tallow (41.8 titre) 90 Coconut oil 10 Fatty matter content 45.45 Neutral silicate 78 Tw 19.10

Hardness Heated to 0.

lb. at'C.

Control Bar 3 3 25. 0 48.9 6 9 26. 7 54.4 7 s .26. 7

We claim:

1. A process of hardening a bar of at least moisture content soap obtained by extruding the soap at a temperature not exceeding C., which comprises heating the bar by means of alternating current to a temperature of at least C. but below that at which the soap becomes no longer form-retaining due to melting and then allowing the bar to cool.

2. A process according to claim 1 in which the soap contains at least 25% moisture.

3. A process according to claim 1 in which the soap is an unfilled soap having a total fatty matter content of 60-65%.

4. A process according to claim 1 in which the soap is a filled soap containing up to moisture.

5. A process according to claim 1 in which the bar is heated by resistance heating.

References Cited in the file of this patent UNITED STATES PATENTS Heald Oct. 24, 1950 FOREIGN PATENTS Great Britain Apr. 24, 1930 Australia Apr. 26, 1944 

